MSMB is the second most abundant protein after prostate specific antigen (PSA) found in semen of healthy men and regulates prostate cell death. It is secreted from semen into the urine. Writing in the October issue of Public Library of Science (PloS) One, the researchers said low levels of MSMB are associated with higher prostate cancer risk.
Prostate cancer, the second most common cause of cancer death among men in the United States, killed an estimated 258,000 men around the world in 2008. Currently, the most widely used prostate cancer test looks for elevated levels of PSA in the blood. However, results of some recent studies have led to some uncertainty about the value of this test. [See the article, Prostate Cancer: To Screen or Not to Screen?]
To determine if MSMB tests could be useful in prostate cancer screening or diagnosis, the researchers took tissue and urine samples from more than 350 men, both with and without prostate cancer, to test MSMB levels and determine whether the men had a particular genetic variation in the section of DNA that regulates the production of MSMB. This genetic variation, or mutation, was identified during previous studies by the researchers and others when they examined the entire genomes of thousands of men both with and without prostate cancer. This common mutation, which results in decreased production of MSMB, was shown to increase men's risk for prostate cancer by about 30%. Up to 40% of men with European ancestry and up to 70% of men with African ancestry have the mutation.
In the latest study, the researchers measured levels of MSMB in the urine of participants and correlated them with levels of PSA in the urine, whether the men had prostate cancer, and whether they had the small genetic change, or mutation. They found reduced levels of MSMB in the urine of men diagnosed with the prostate cancer, especially those with aggressive disease. These findings suggest that levels of MSMB protein in urine could form the basis for a new test to help identify men at greater risk of developing the disease, say the researchers. It could potentially be used alongside PSA testing to improve detection of prostate cancer and for monitoring progression of the disease.
PSA screening tests are far from ideal because nonfatal cancers and benign conditions can increase PSA levels. A U.S. study published last year found that routine PSA prostate screening has resulted in prostate tumor diagnoses in more than one million American men who might otherwise have suffered no ill effects from them. An enlarged prostate, a noncancerous condition, can boost PSA levels. Some hormones altered by particular prostate cancer treatments can also interfere with PSA production and thus testing to monitor progression of the disease. In contrast, MSMB levels appear to be largely unaffected by an enlarged prostate or hormones.
But doctors won't be offering men MSMB tests any time soon. According to a published news report, researcher Hayley Whitaker predicts that it will take his team five years to develop a test for use in clinics. In the U.S., such a test would also be subject to a lengthy Food and Drug Administration approval process before doctors could offer it.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Press release. Urine protein could pave the way for new prostate cancer test. Cancer Research UK. Available online at http://info.cancerresearchuk.org/news/archive/pressrelease/2010-10-14-urine-protein-cancer-test through http://info.cancerresearchuk.org. Issued October 13, 2010. Accessed October 20, 2010.
Kate Kelland. Protein urine test may signal prostate cancer. Reuters. Available online at http://news.yahoo.com/s/nm/20101013/hl_nm/us_cancer_prostate_urine through http://news.yahoo.com. Published October 13, 2010. Accessed October 20, 2010.